fix: game audio persistence and editor perf

- Keep game/campaign audio assets referenced (no prune)
- Flush pending project save on quit/switch/export to avoid losing campaignAudios
- Control: prevent game music restarts on scene changes; allow always-on controls; handle autoplay-after-scene-audio
- Editor: reduce ReactFlow churn with stable scene card map; lazy/async image decode
- Add contract/unit tests and update test script

Made-with: Cursor

app/renderer/editor/EditorApp.module.css

@@ -100,6 +100,10 @@
   height: 14px;
 }
 
+.spacer18 {
+  height: 18px;
+}
+
 .sidebarScroll {
   overflow: auto;
   padding-right: 2px;
@@ -408,7 +412,7 @@
   overflow: hidden;
   background: var(--color-overlay-dark-3);
   aspect-ratio: 16 / 9;
-  max-height: 140px;
+  width: 100%;
   display: flex;
   align-items: center;
   justify-content: center;